1. Field of the Invention
The present invention relates to a plasma display panel (PDP) and, more particularly, to a composition of glass for PDP and its fabrication method.
2. Description of the Background Art
In general, a plasma display panel (PDP) device receives much attention as a next-generation display device together with a thin film transistor (TFT), a liquid crystal display (LCD), an EL (Electro-Luminescence) device, an FED (Field Emission Display) and the like.
The PDP is a display device using a luminescent phenomenon according to an energy difference made when red, green and blue fluorescent materials are changed from an excited state to a ground state after being excited by 147 nm of ultraviolet rays which are generated as a He+X3 gas or N3+X3 gas is discharged from a discharge cell isolated by a barrier rib.
Thanks to its properties of facilitation in manufacturing from a simple structure, a high luminance, a high light emitting efficiency, a memory function, a high non-linearity, a 160° or more optical angular field and the like, the PDP display device is anticipated to occupy large-scale display device markets.
A structure of the conventional PDP will now be described with reference to FIG. 1.
FIG. 1 is a sectional view showing a structure of a conventional PDP.
As shown in FIG. 1, the conventional PDP includes: a lower insulation layer 20 formed on a lower glass substrate 21; an address electrode 22 formed at a predetermined portion on the lower insulation layer 20; a lower dielectric layer 19 formed on the address electrode 22 and the lower insulation layer 20; an isolation wall 17 defined in a predetermined portion on the lower dielectric layer 19 in order to divide each discharging cell; a black matrix layer 23 formed on the isolation wall 17; a fluorescent layer 18 formed with a predetermined thickness on the side of the black matrix layer 23 and the isolation wall 17 and on the lower dielectric layer 19, and receiving ultraviolet ray and emitting each red, green and blue visible rays; a glass substrate 11; a sustain electrode 12 formed at a predetermined portion on the upper glass substrate 11 in a manner of vertically intersecting the address electrode 22; a bus electrode 12 formed on a predetermined portion on the sustain electrode 12; an upper dielectric layer 14 formed on the bus electrode 13, the sustain electrode 12 and the upper glass substrate 11; and a protection layer (MgO) 15 formed on the second upper dielectric layer 14 in order to protect the upper dielectric layer 14.
The operation of the conventional PDP will now be described.
First, as the upper glass substrate 11 and the lower glass substrate 21 of the conventional PDP, an SLS (Soda-Lime Silicate) glass substrate is used.
The lower insulation layer 20 is positioned on the lower glass substrate 21, the SLS glass substrate, and the address electrode 22 is positioned on the lower insulation layer 20.
The lower dielectric layer 19 positioned on the address electrode 22 and the lower insulation layer 20 blocks visible rays emitted toward the lower glass substrate 21.
In order to increase the luminous efficacy, a dielectric layer having a high reflectance is used as the lower dielectric layer 19. The lower dielectric layer 19, a translucent dielectric layer with a reflectance of 60% or above, minimizes loss of light.
The fluorescent layer 18 is formed by laminating in a sequential order of red, green and blue phosphor materials. A specific wavelength of visible ray is emitted depending on an intensity of an ultraviolet ray according to plasma generated between the isolation walls 17.
Meanwhile, at a lower surface of the upper glass substrate 11, the SLS glass substrate, there are formed the sustain electrode 12 positioned to vertically intersect the address electrode 22 and the bus electrode 13 positioned on the sustain electrode 12. And upper dielectric layer having an excellent light transmittance is positioned on the bus electrode 13.
The protection layer 15 is positioned on the upper dielectric layer 14 in order to prevent the upper dielectric layer 14 from being damaged due to generation of plasma. Herein, since the upper dielectric layer 14 is directly contacted with the sustain electrode 12 and the bus electrode 13, it must have a high softening temperature in order to avoid a chemical reaction with the sustain electrode 12 and the bus electrode 13.
Thereafter, as the upper plates 11˜15 and the lower plates 19˜22 are bonded by a seal material 16, a PDP is completely formed.
Of the formed structures, the isolation wall 17, the lower dielectric layer 19, the upper dielectric layer 14, the seal material 16 are glass compositions containing a large amount of Pb.
In addition, the fabrication process of the isolation wall 17, the lower dielectric layer 19, the upper dielectric layer 14 and the seal material 16 may have a vital influence on a human body.
Moreover, discarding of the glass composition may cause an environmental pollution.
Especially, as the move of regulating use of materials detrimental to the human body and the environment is becoming more active worldwide, development of an unleaded dielectric materials that may substitute the dielectric of the PDP containing a large volume of Pb is actively made.
The conventional unleaded glass composition includes alkali metal-oxide to lower a softening temperature of glass, but there has been reported that movement of alkali metal ion during discharging makes a bad influence on the discharge characteristics.
In an effort to solve the problem of the unleaded glass composition containing the alkali metal-oxide, an unleaded non-alkali dielectric comprising ZnO—B2O3—BaO has been proposed, which, however, has a problem that a glass structure is so unstable that a transition point of glass contained in the unleaded non-alkali dielectric is too high or a phase separation of glass occurs.
In addition, in order to drop the softening temperature, the amount of Bi2O3 is added by 60˜50 wt %, but in this case, a problem arises that a cost of the dielectric material is increased due to the high-priced Bi2O3 and a luminous efficacy is degraded as a discharge current is increased due to the high electric pemittivity.
Other conventional PDPs and their fabrication methods are disclosed in the U.S. Pat. No. 5,838,106 issued on Nov. 17, 1998, a U.S. Pat. No. 6,242,859 issued on Jun. 5, 2001, and a U.S. Pat. No. 6,599,851 issued on Jul. 29, 2003.
As stated above, the glass composition used for the PDP in accordance with the conventional art has the following problems.
That is, first, the glass composition includes a large amount of Pb which is critical to the human body and the environment, and the unleaded glass composition adopting the alkali metal-oxide intended not to use Pb has such degraded discharge characteristics.
Second, the glass composition having ZnO—B2O3—BaO as a primary component, which is proposed as an unleaded non-alkali dielectric has a high softening temperature, causes a phase separation, and has an unstable glass structure.
Third, since the large amount of Bi2O3 is contained in the glass composition to lower the softening temperature, the fabrication cost of the glass composition is increased, and the electric permittivity of glass is so high that the luminous efficacy is degraded.